I have a couple routes in the works, and I jump from one to the other. One of my routes is the original route I started in Dec 2003 in TRS2004. This route is going through a major rebuild with large portions being replaced and or upgraded with much, much better building techniques and large sections being replaced with actual DEMs as these look better than my rather poor hand sculpting, which was the only way back then.
Another route I have had in the works for a few years now is my Cape Anne Transit route, and is a rework of George Fisher's idea of a small short line in and around the Gloucester and Rockport area in Massachusetts. George's original route focused on serving the docks in and around Gloucester Harbor. I took his route a number of years ago and electrified it, and in the process turned it from a freight short line into an electrified passenger route with diesel freights. My Gloucester Terminal Electric route, this modified version of George's route, has since been frozen with no new changes. I still enjoy driving the session I created for it with the rather unusually long portal freights going between Rockport and Boston, the MBTA commuter trains, and then the ongoing trolley and local freight operations. There are days when I've spent many hours switching freight cars with the AI busily driving their trams along the electrified route.
But continuing that theme, my now new version is based 100% on a DEM of the Cape Anne Peninsula. On this route I have worked tracks along the back road (MA Rt. 127 and 127a) towards Annisquam, Wingersheek Beach, as the line serves these little communities on the north, as well as branches to Magnolia via Ravenscroft Woods, West Gloucester, and lines to Eastern Point, and Rockport including the actual Rockport branch of the MBTA, except I'll run freights too because I can. During my building, and aerial photo searching, I have discovered the ROWs of old disconnected quarry railroads which once dotted the peninsula. On my route, I have connected these together in the rail system and made some of them are active since in real life they have become reservoirs and large wooded parks as they've long lived out their usefulness as a quarries.